On Sun, Oct 18, 2009 at 12:57 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > Robert Haas <robertmh...@gmail.com> writes: >> You could probably convince me that a merge join is not going to be >> too useful (how often can you want a merge join on the inner side of a >> nested loop? > > Why not? As Andrew pointed out, what we're really trying to accomplish > here is consider sub-join plans that are parameterized by a value > obtained from an outer relation. I think we shouldn't artificially > limit what we consider.
Am I understanding you right that a typical case of this might be something like nested loop index scan expecting 1 record merge join index scan on partial index where col = outer.foo and col2 between a and b some other scan or nested loop index scan expecting 1 record merge join index scan on <col1,col2> where col1 = outer.foo and col2 between a and b some other scan Ie, where the nested loop is a degenerate nested loop which only expects a single value and provides a parameter which allows some partial index to work or allows for some other index scan by providing a higher order key element? -- greg -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers